Temporal Variability of CO<Subscript>2</Subscript> and N<Subscript>2</Subscript>O Flux Spatial Patterns at a Mowed and a Grazed Grassland

Spatial patterns of ecosystem processes constitute significant sources of uncertainty in greenhouse gas flux estimations partly because the patterns are temporally dynamic. The aim of this study was to describe temporal variability in the spatial patterns of grassland CO₂ and N₂O flux under varying environmental conditions and to assess effects of the grassland management (grazing and mowing) on flux patterns. We made spatially explicit measurements of variables including soil respiration, aboveground biomass, N₂O flux, soil water content, and soil temperature during a 4-year study in the vegetation periods at grazed and mowed grasslands. Sampling was conducted in 80 × 60 m grids of 10 m resolution with 78 sampling points in both study plots. Soil respiration was monitored nine times, and N₂O flux was monitored twice during the study period. Altitude, soil organic carbon, and total soil nitrogen were used as background factors at each sampling position, while aboveground biomass, soil water content, and soil temperature were considered as covariates in the spatial analysis. Data were analyzed using variography and kriging. Altitude was autocorrelated over distances of 40–50 m in both plots and influenced spatial patterns of soil organic carbon, total soil nitrogen, and the covariates. Altitude was inversely related to soil water content and aboveground biomass and positively related to soil temperature. Autocorrelation lengths for soil respiration were similar on both plots (about 30 m), whereas autocorrelation lengths of N₂O flux differed between plots (39 m in the grazed plot vs. 18 m in the mowed plot). Grazing appeared to increase heterogeneity and linkage of the spatial patterns, whereas mowing had a homogenizing effect. Spatial patterns of soil water content, soil respiration, and aboveground biomass were temporally variable especially in the first 2 years of the experiment, whereas spatial patterns were more persistent (mostly significant correlation at p < 0.05 between location ranks) in the second 2 years, following a wet year. Increased persistence of spatial patterns after a wet year indicated the recovery potential of grasslands following drought and suggested that adequate water supply could have a homogenizing effect on CO₂ and N₂O fluxes.     

The determination of urinary fluoride/creatinine ratio (Q) in monitoring fluoride intake

Linear correlation (r = 0.6811, p less than 0.001) was found between the 24 hour urinary excreted fluoride quantity and fluoride/creatinine ratio (Q) of the morning urine sample of 21 school children living in a children's home in Hungary. The mean value of fluoride/creatinine ratio (Q) in groups of children from eight different parts of Hungary, also showed linear correlation (r = 0.9720, p less than 0.001) with the measured fluoride concentration of drinking water. The urinary fluoride/creatinine ratio (Q) seems sufficiently informative for controlling fluoride intake in the course of caries preventive field studies.     

Binding site of salsolinol: its properties in different regions of the brain and the pituitary gland of the rat

It has been recently shown that salsolinol (SAL) is present in the hypothalamic neuroendocrine dopaminergic (NEDA) system and appears to be a selective and potent stimulator of prolactin (PRL) secretion in the rat. Furthermore, the lack of interference of SAL with 3H-spiperone binding in the striatum and the anterior lobe (AL) of the pituitary gland has been also demonstrated. These data clearly indicate that SAL does not act at the dopamine (DA) D(2) receptors, and suggest that SAL supposedly has a binding site through which the secretion of PRL may be affected. Therefore, binding of 3H-SAL to different regions of the central nervous system (CNS) has been investigated. Specific and saturable binding has been detected in the striatum, cortex, median eminence and in the hypothalamus as well as in the AL and the neuro-intermediate lobe (NIL) of the pituitary gland. K(D) values of the bindings were in the nanomolar range in all tissue tested. 3H-SAL displacing activity of several agonists and antagonists of known DA receptors have also been tested. It has been found that DA and in a lesser extent, apomorphine could displace 3H-SAL, but other DA receptor specific ligands have not been able to affect it. Furthermore, several pharmacologically active compounds, selected on the basis of their influence on DA synthesis, transport mechanisms and signal transduction, have also been tested. Neither mazindol (a selective DA transporter inhibitor) nor clonidine (an alpha(2)-adrenoreceptor agonist) could alter SAL binding. At the same time, L-dopa, carbidopa, benserazide and alpha-methyldopa were able to displace 3H-SAL. The possible changes in SAL binding due to physiological and pharmacological stimuli, like suckling stimulus and reserpine pretreatment (that blocks vesicular monoamine transport in DA terminals), respectively, have also been investigated. In the NIL of the pituitary gland and in the median eminence of the hypothalamus the binding decreased following 10 min of suckling stimulus compared to the binding detected in the same tissues obtained from mothers separated from their pups for 4h and not allowed to be suckled. At the same time, there were no changes in the binding at the AL and striatum. Following reserpine pretreatment that has completely prevented PRL releasing effect of SAL, the binding was significantly augmented. These results support our assumption that SAL should have specific binding sites through which it can affect PRL secretion. Furthermore, it clearly suggests that it may regulate DAergic neurotransmission of NEDA neurons by an altered intracellular or intraterminal synthesis and/or distribution of hypophysiotropic DA.     

Fertile wheat (Triticum aestivum L.) regenerants from protoplasts of embryogenic suspension culture

We report regeneration of fertile, green plants from wheat (Triticum aestivum L. cv. Aura) protoplasts isolated from an embryogenic suspension initiated from somatic early-embryogenic callus. The present approach combines the optimization of protoplast culture conditions with screening for responsive genotypes. In addition to the dominant effect of the culture media, the increase in fresh mass and the embryogenic potential of somatic callus cultures varied considerably between the various genotypes tested. Establishment of suspension cultures with the required characters for protoplast isolation was improved by reduction of the ratio between cells and medium and by less frequent (monthly) transfer into fresh medium. A new washing solution was introduced to avoid the aggregation of protoplasts. However, the influence of the culture medium on cell division was variable in the different genotypes. We could identify cultures from cultivar Aura that showed approximately a 9% cell division frequency and morphogenic response. The protoplast-derived microcolonies formed both early and late-embryogenic callus on regeneration medium and green fertile plants were obtained through somatic embryogenesis. The reproducibility of plant regeneration from protoplast culture based on the cultivar Aura was demonstrated by several independent experiments. The maintenance of regeneration potential in Aura suspension cultures required establishment of new cultures within a 9-month period.     

Imaging of pediatric brain tumors using somatostatin analogue 111Ih-DTPA-D-Phe1-octreotide

Malignant solid tumors and leukemias are the second most common causes of death in childhood. The most frequent pediatric solid tumors are brain tumors. Brain tumors, especially medulloblastoma should be treated by surgery, irradiation and chemotherapy. However, chemotherapy has only moderate effect. Pediatric brain tumors, especially medulloblastomas, express somatostatin receptors. The aim of this study was the investigation of the expression of somatostatin receptors in pediatric brain tumors for diagnostic and therapeutic purpose. Fifty-six scintigraphic imagings (111In-DTPA-D-Phe1-octreotide) made in 45 children treated with brain tumor at the Unit of Oncology of the 2nd Department of Pediatrics, Semmelweis University. The diagnosis was medulloblastoma in 21 cases (46.7%). MRI scans have been performed parallel with the Octreoscan images. Octreoscan images were positive in 27 of 56 (48.2%) cases. The 27 positive Octreoscan images consisted of 16 medulloblastomas, 4 ependymomas, 4 astrocytomas and 3 glioblastomas. In 37 (66.1%) cases the results of Octreoscans were the same as those of the MRI scans. However, in 19 scans (33.9%) the outcome was different. Octreoscan imaging is not suitable for differential diagnosis in pediatric brain tumors, including medulloblastomas. Isotopes specifically binding to the somatostatin receptors (111In-DTPA-D-Phe1-octreotide) can be applied in medulloblastomas for diagnosis and follow-up treatment. In Octreoscan-positive tumors the Octreoscan images establish the opportunity to somatostatin analogue and/or specifically targeted radiation therapies.     

Towards the co‐ordination of terrestrial ecosystem protocols across European research infrastructures

The study of ecosystem processes over multiple scales of space and time is often best achieved using comparable data from multiple sites. Yet, long‐term ecological observatories have often developed their own data collection protocols. Here, we address this problem by proposing a set of ecological protocols suitable for widespread adoption by the ecological community. Scientists from the European ecological research community prioritized terrestrial ecosystem parameters that could benefit from a more consistent approach to data collection within the resources available at most long‐term ecological observatories. Parameters for which standard methods are in widespread use, or for which methods are evolving rapidly, were not selected. Protocols were developed by domain experts, building on existing methods where possible, and refined through a process of field testing and training. They address above‐ground plant biomass; decomposition; land use and management; leaf area index; soil mesofaunal diversity; soil C and N stocks, and greenhouse gas emissions from soils. These complement existing methods to provide a complete assessment of ecological integrity. These protocols offer integrated approaches to ecological data collection that are low cost and are starting to be used across the European Long Term Ecological Research community.     

Resource transport between ramets alters soil resource pattern: a simulation study on clonal growth

Clonal plants spread horizontally, and can transport nutrients between ramets. Decaying biomass feeds back nutrients into the soil, but importantly, the place of deposition may differ from the place of uptake. To our knowledge, the present model is the first attempt to couple population dynamics with resource dynamics with the consideration of lateral transport. The simulations start from various initial resource patterns. Six types of clonal plants are compared, which differ in the birth and survival rates of ramets. Size of the ramet population and the amount of translocated resource are recorded over time. In addition, we consider the pattern of gaps in the canopy of the clonal plant from the aspect of two colonizer species: a strong and a weak competitor. The results suggest that the most important factor determining the impact of a clonal plant on its environment is ramet survival; the rate of ramet production is only secondary. Phenotypic plasticity in the production of ramets does not appear to be important: it has only minor effect on resource translocation and on the availability of colonizable gaps.